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Microsoft VSS Troubleshooting

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Ben
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Microsoft's Volume Shadow Copy is probably amongst the most complex functions of the Windows operating system; hence, if it breaks it is a time consuming process to repair.

Symptoms of a Volume Shadow Copy Malfunction

  1. Very long (or seemingly indefinite) VSS snapshot generation time with intensive hard drive activity.
  2. VSS errors reported in the Event Viewer (click start and search Event Viewer in search box to open)
  3. VSS errors reported by Microsoft's Volume Shadow Copy tool vssadmin
  4. VSS fails to create snapshots.

Contents: 

 

VSS Repair Strategy #1 - Available Disk Space and Reboot

  1. Check your free disk space on ALL volumes/partitions on the PC where NovaBACKUP is installed. If disk space is too low, VSS will cause the backups to fail if "Open File Backup" is enabled, which it is by default in NovaBACKUP.  VSS utilizes disk space on your partitions, not just the C: drive, to cache data.  VSS alone can utilize the remaining disk space on your partition and you would not even know it unless you knew about the command line functions to check that disk space usage for VSS.
  2. Reboot. For some reason, servers that haven't been rebooted in a while can cause VSS to malfunction. As all Microsoft veterans know, you need to reboot regularly as a preventive and cleanup measure for your system.

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VSS Repair Strategy #2 - System File Check

Run the System File Checker (sfc) with these steps:

  1. Click the Start orb and then type cmd in the Search programs and files field.
  2. In the results area, right-click cmd.exe, and then click Run as administrator. You will be prompted to type the password for an administrator account. Click Continue if you are the administrator or type the administrator password. Then, click Continue.
  3. At the command prompt, type "sfc /verifyonly", and then press ENTER. This will just scan the system. If it finds issues and you need to repair, run "sfc /scannow".

The scan may take some time, so be patient. Windows will repair any corrupted or missing files that it finds

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VSS Repair Strategy #3 - VSS shadows

Open vssadmin from the command line (run cmd as administrator).

Enter vssadmin delete shadows /all to clean up any dead VSS snapshots. Some defect systems accumulate hundreds of VSS snapshots that persist in the system and cause Windows to become unresponsive.

If vssadmin /delete shadows all does not work, you will need to use DISKSHADOW: 

  1. diskshadow [enter]
  2. delete shadows all [enter]

Enter vssadmin list writers and check for errors. If you receive any errors for one VSS writer, you may need to fix that particular VSS writer. It is common to receive writer errors caused by Microsoft's Virtual Server 2005 VSS writer.

If you see a VSS writer error, try the following:

Restart the services:

  • COM System Application Service
  • Distributed Transaction Coordinator Service
  • Volume Shadow Copy Service

and also restart the affected VSS writer service, for example Virtual Server 2005 VSS writer or Hyper-V VSS writer. How To Resolve VSS Writer Errors Without Rebooting

Check the Event Viewer for any additional error information logged by that VSS writer.

Run again vssadmin list writers to check if the above resolved the problem. If it didn't follow with the next strategy below:

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VSS Repair Strategy #4 - VSS Command Line Troubleshooting

You can try to re-register all VSS and COM components by following our FAQ on VSS Command Line Troubleshooting

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VSS Repair Strategy #5 - Complete Uninstall and Reinstall of all backup software

Uninstall all backup software on your computer, including Windows Backup if it's installed. You don't need to uninstall NovaBACKUP because NovaBACKUP doesn't contain or install any VSS writers; however, we have seen VSS writers of other backup software manufacturers cause system instability and errors.

After all other backup tools have been uninstalled, open the Registry Editor (regedit) as administrator and check the following branch: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS\Providers

Underneath that key you should only find Microsoft Software Shadow Copy Provider 1.0 and no other VSS writer. If you do find another, it may be a residue registry entry of a previous backup software installation. You can save the entry by exporting the entire registry to a file (right click and select Export) and then it's safe to delete the entire branch entry underneath HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\VSS\Provider.

Then reboot and try again running vssadmin list writers to confirm the problem has been resolved.

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VSS Repair Strategy #6 - Virtual machines

If the PC or server you are using is a virtual machine host, you need to install the latest VMware Tools (for VMware), Virtual Machine Additions (Virtual Server), on each virtual machine.

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VSS Repair Strategy #7 - COM Subscription corruption

Your computer may have a corrupt COM subscription information. Open the registry editor (regedit) and navigate to:

HKLM\Software\Microsoft\EventSystem\{26c409cc-ae86-11d1-b616-00805fc79216}

Then delete the Subscriptions key and reboot the machine.

A subsequent call in the command prompt should show no more errors: vssadmin list writers

This VSS repair strategy appears to work well when the System Writer is reporting an error. The Event Viewer may be reporting this or a similar error:

Writer Class Id: {e8132975-6f93-4464-a53e-1050253ae220}
Writer Name: System Writer
Writer Instance ID: {34162f4c-59ff-468e-848d-cb4b3d8dd7dc}

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VSS Repair Strategy #8 - Windows Update

Install the latest Service Packs and Updates through Windows Update.

Check Microsoft's Support for hot fixes and other updates to repair VSS.

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VSS Repair Strategy #9 - Additional Non-Microsoft VSS Provider(s)

Problem:

You attempt to perform a backup of open files (any plugin or Image Backup, in this case), and it appears to work, but does not write all expected data.

The issue is because Symantec or other software, has installed a VSS Provider. Such as:

Provider name: 'Symantec Software VSS Provider'
   Provider type: Software
   Provider Id: {262b716e-bb23-41b5-aaef-e2c15e767167}
   Version: 1.0

In Event Viewer after you started the most recent Image Backup attempt, the Symantec VSS writer is intercepting the VSS operation:
Context: Provider ID: {} is pointing to another VSS Provider instead of the Microsoft VSS Provider.

Error    MM/DD/YY HH:MM:SS    VSS    22    None

Volume Shadow Copy Service error: A critical component required by the Volume Shadow Copy service is not registered. This might happened if an error occurred during Windows setup or during installation of a Shadow Copy provider. The error returned from CoCreateInstance on class with CLSID {790f2886-9889-4c99-8ef5-531add05d044} and Name SW_PROV is [0x80040154, Class not registered
]. 

Operation:
   Obtain a callable interface for this provider
   List interfaces for all providers supporting this context
   Check If Volume Is Supported by Provider

Context:
   Provider ID: {262b716e-bb23-41b5-aaef-e2c15e767167}
   Class ID: {790f2886-9889-4c99-8ef5-531add05d044}
   Snapshot Context: 0
   Snapshot Context: 0
   Execution Context: Coordinator
   Provider ID: {00000000-0000-0000-0000-000000000000}
   Volume Name: \\?\Volume{ec87cfc6-061c-11e1-97aa-806e6f6e6963}\

 

Resolution:

Remove the extra non-Microsoft VSS Provider(s) 

To remove a VSS Provider that is interfering with backup operations: 

The following steps need to be performed using the Windows Registry Editor "regedit"

  • Take a backup of registry
  • Delete the Symantec VSS provider GUID from the following registry location: HKey_Local_Machine\system\CurrentControlSet\Services\VSS\Providers
  • reboot server, take backup.

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